About £120m a year is being spent on NHS surgery that appears to offer little medical benefit, finds a survey of patient responses, which suggests that 29% of those having groin hernia operations and 24% of those given surgical treatment for varicose veins, report no improvement, or even a worsening, in their conditions.

The survey, carried out by the Office of Health Economics, and reported in the Health Services Journal, examined data from the new patient reported outcome measures (Proms) process.

For hip and knee replacements, the proportions of people reporting no improvement were smaller: 9% of hip patients and 18% of knee patients.

Extrapolated to the total number of the four procedures carried out every year by the NHS, as much as £120m is being spent on operations that leave patients feeling no better.

The study also found that operations were carried out on a significant number of people who had reported no problem before surgery.

The Department of Health said: "Procedures are not unnecessary simply because patients do not have pain. They can be preventive or improve quality of life or mobility. To use a relatively small sample and apply it across the NHS – where a million patients are treated every 36 hours – is misleading, especially when the data ­concentrates on the outcome of surgery, not the reasons a procedure has been ­carried out."